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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108370] gcc doesn't merge bitwise-AND if an explicit
 comparison against 0 is given
Date: Wed, 11 Jan 2023 14:24:45 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108370

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
ifcombine seems to assume that

     D.1987_7 =3D op0 & 1;
     if (D.1987_7 !=3D 0)

is canonical but we see

  _9 =3D (_Bool) _6;
  if (_9 !=3D 0)

instead.  That's already the form introduced by inlining from

_Bool bio_flagged (struct bio * bio, unsigned int bit)
{
  short unsigned int _1;
  unsigned int _2;
  unsigned int _3;
  unsigned int _4;
  _Bool _8;

  <bb 2> :
  _1 =3D bio_6(D)->bi_flags;
  _2 =3D (unsigned int) _1;
  _3 =3D _2 >> bit_7(D);
  _4 =3D _3 & 1;
  _8 =3D _4 !=3D 0;
  return _8;

and

  <bb 2> :
  _1 =3D bio_flagged (bio_7(D), 0);
  if (_1 !=3D 0)
    goto <bb 4>; [INV]
  else
    goto <bb 3>; [INV]=